In many technical fields, in particular for aeronautical applications, it is often necessary to have couplings of mechanical shafts that may break when these couplings are subjected to torques consisting of opposing forces that exceed a predetermined value. This functionality makes it possible to protect the components downstream of these couplings. To do this, providing twist-breakable sections on the shaft lines is known. Such a twist-breakable section has the specific feature of being able to break when it is subjected to the action of a torque consisting of opposing forces above a predetermined value.
A known solution for forming a twist-breakable section on a shaft line involves using a solid shaft that has a local reduction in its diameter so that this part having a smaller diameter can break when the torque exceeds a predetermined value.
One of the drawbacks of this solution is that, when the breakable section breaks, it is necessary to replace the entire shaft, which, for some applications, requires dismantling all the components connected to the shaft. This is particularly the case with cooling units of turbine engines. A cooling unit comprises a pinion and an impeller mounted in cantilever on the shaft carrying the pinion. If the breakable section formed on the shaft by local reduction in the diameter breaks, it is necessary to remove the impeller and the reducer module connected to the cooling unit in order to be able to replace the drive shaft. This makes maintaining and replacing such a breakable section complicated and not very practical to implement.
Furthermore, if the maximum torque is relatively low, which is the case for example with cooling-unit impellers, the breakable section may be small, which may impose significant installation constraints (in order not to stress said breakable section) and operating constraints (dynamics of the shaft line, movement under maneuvering loads).
Another solution for providing a twist-breakable section on a shaft line involves using a hollow shaft having a local reduction in material on its internal or external wall. This solution still has the drawbacks of the previous solution. In addition, the sizing for the breakage torque of this solution gives thicknesses that are too small to be properly controlled.
Another solution involves shrinking one mechanical component onto the other and controlling the sliding force. One of the drawbacks of this solution is the difficultly in properly controlling the sliding in the operating temperature range of the components concerned. This drawback makes this solution particularly unsuited to turbine-engine cooling units.
There is therefore a need to have an improved solution for providing a twist-breakable section in a mechanical coupling of components in a turbine engine. Such a need is expressed in particular, but not solely, for uses in turbine-engine cooling units.
In particular there is a need to have a solution that allows a replacement of this breakable section without any particular difficulties and in particular without requiring complete dismantling of the mechanical components affected by this coupling.